Dental handpiece having a body formed from a single piece and comprising an electrical and elastic linking component between the mechanical transmission components and the head of the instrument

ABSTRACT

The invention relates to a dental handpiece ( 1 ) of the type comprising mechanical components, in particular a tool-holder assembly for the attachment and rotational driving of a dental instrument about a drive axis ( 6 ) and an assembly for the transmission of movement, said mechanical components being mounted in the interior of a body ( 2 ) having a head ( 4 ) and a handle ( 3 ), characterized in that it comprises means of electrical connection between the mechanical components of the handle and the head of the instrument, which means are constituted by an elastic and electrically conducting connecting device.

The invention relates to a new type of dental handpiece.

Previously disclosed dental handpieces are of two types, straight handpieces and counter-angled handpieces.

In the case of counter-angled handpieces, the body consists of a handle exhibiting an elbow and a head.

This structure results in an embodiment which requires at least two parts for the body, and very often three, in order to permit the assembly of the internal components, which also requires a plurality of bearings, at least three in number.

It will be appreciated that this type of design does not permit a reduction in costs to any significant degree.

A first object of the invention is to propose a new concept for the structure of handpieces that is capable of replacing the current concept of handpieces and permits the production of the body in a single piece, whether for handpieces that are driven by mechanical means or for handpieces that are driven by an air turbine.

This object is achieved by the invention, which consists of a dental handpiece of the type comprising mechanical components, in particular a tool-holder assembly for the attachment and rotational driving of a dental instrument about a drive axis and an assembly for the transmission of movement, said mechanical components being mounted in the interior of a body having a head and a handle, characterized in that the body is formed from a single piece or an envelope, of which one part serves as a handle, and the other part constitutes a head, which head comprises a first housing opening out with at least one opening so dimensioned as to permit the introduction of the component parts of the head and their assembly in the interior of the latter, which handle comprises a second longitudinal housing having a rectilinear axis and opening out, on the one hand, at the extremity of the handle via an opening and, on the other hand, in the first housing via a lateral opening, which opening is so dimensioned as to permit the introduction of the internal component parts of the handle and their assembly in the interior of the latter.

In accordance with a variant embodiment, the handpiece comprises electrical connection means constituted by a chain of component parts for the mechanical transmission of the rotational movement assuring the transmission of the movement and the electrical energy from a connection provided at the extremity of the handle, in order to interact with an external motor, and as far as the instrument.

In accordance with another variant, it comprises electrical connection means constituted by a conducting wire.

In accordance with another variant, it comprises an elastic connection component for the purpose of providing an electrical connection between the mechanical transmission component parts and the head of the tool.

In accordance with another variant, the head contains a turbine, and the body of the handpiece comprises fluid channels that are necessary for its function.

The interior housing of the head is preferably so adapted as to receive a tool-holder assembly composed of mechanical transmission component parts of the head, and as to receive a means of tightening and releasing the tool or the instrument, said housing opening out onto the head via an opening that is closable by means of a stopper or a cap, or by means of a push-button.

The handpiece preferably comprises an arrangement for the attachment of a dental instrument to a tool-holder assembly for the attachment and rotational driving of a dental tool or instrument about a driving axis, said tool-holder assembly being integrated into a head of a dental handpiece and connected to an assembly for the transmission of movement integrated in a handle of the said handpiece and composed principally of a deformable and elastic means of tightening and releasing in the form of a belt, of which at least one part exhibits a section adapted to engage in a groove or an annular slot that is provided in the upper part of the instrument and is adapted to retain the said instrument by tightening of the instrument, said means of tightening and releasing also comprising means for the application of releasing forces for canceling the tightening forces for the purpose of releasing the instrument.

Said attachment arrangement is preferably detachable in relation to the tool-holder.

In accordance with one variant, the belt made of a deformable, elastic material exhibits a form that is essentially that of a parallelogram having a central zone provided for the purpose of retaining the head of the instrument tightly in place at the level of a slot.

In accordance with another variant, the elastic, deformable belt exhibits the form of a split ring or a split annular clip comprising an annular shoulder so adapted as to engage in an annular slot in the instrument and a conical part intended to interact with a complementary conical part of a push-button.

In accordance with the execution variant and/or the operating speed of the tool, the attachment arrangement may comprise a push-button, which may or may not be integral with the tool-holder, and may be capable of being retained, for example by clipping, in an opening in the head.

The invention will be appreciated more easily with the help of the description below, in conjunction with which reference is made to the following accompanying Figures:

FIG. 1: a general view in three dimensions of a handpiece in accordance with the invention,

FIG. 2: a view as a longitudinal section of the handpiece in FIG. 1,

FIG. 3: a view as a partial longitudinal section of a non-restrictive embodiment of the invention,

FIG. 4: a three-dimensional representation and a partial section of another non-restrictive embodiment comprising a means of tightening and releasing in the form of a lozenge-shaped elastic belt capable of being released manually,

FIG. 5: a view as an axial section of the view in FIG. 4,

FIG. 6: a view as a partial transverse section of the head in FIG. 4, illustrated at the level of the elastic belt,

FIG. 7: a three-dimensional representation and a partial section of the head in FIG. 4,

FIG. 8: a view as an axial section of another non-restrictive embodiment comprising a means of tightening and releasing in the form of an elastic belt capable of being released by the actuation of a push-button,

FIG. 9: a three-dimensional representation and a partial section of the embodiment in FIG. 8,

FIG. 10: a three-dimensional representation of the elastic belt in FIGS. 8 and 9,

FIG. 11: a view as an axial section of another non-restrictive embodiment comprising a means of tightening and releasing in the form of a split ring,

FIGS. 12 and 13: a three-dimensional representation of the push-button in FIG. 11,

FIGS. 14 and 15: a three-dimensional representation of a means of tightening and releasing in the form of a split annular clip in FIG. 11,

FIG. 16: a three-dimensional representation of a push-button in FIG. 3,

FIG. 17: a variant embodiment of FIG. 3 comprising an elastic and conducting connection component part.

General Concept of the Body of the Handpiece.

Reference is made in the first instance to the non-restrictive examples in FIGS. 1 to 3.

A handpiece (1) in accordance with the invention consists of a body (2) in a single piece comprising one part serving as a handle (3) having a rectilinear axis, and one part constituting a head (4), for the attachment and driving of an instrument (5) as claimed in a driving axis (6) capable of being aligned with the axis (7) of the handle or capable of forming a predetermined angle with the latter, lying between 90 and 180°, and preferably lying between 100 and 130°, as illustrated in the non-restrictive example in the Figures.

The body is formed by an envelope (8) or external casing, which may or may not be in a single piece, which may be electrically insulating and capable, for example, of being produced in a polymer, thermoplastic or thermosetting material (preferably polyether-ether ketone, abbreviated to PEEK in the rest of the text) incorporating the mechanical component parts of the handle and the head together with electrical connection means, ensuring the transmission of the movement and the electrical energy from a connection (9) provided at the extremity of the handle in order to interact with an external motor, not illustrated here, as far as the instrument (5) secured in the head (4).

The counter-angle handpiece (1) in accordance with the invention represented in FIGS. 1 to 3 exhibits two axes (6) and (7) enabling the potential for friction inherent in each bearing to be limited in order to guarantee the most stable possible output, for which reason, in this case, ball bearings are also integrated in the envelope (8). An arrangement of the counter-angle handpiece of this kind lends itself particularly well to root canal treatments (endodonty) with an apex locator.

A handpiece in accordance with the invention that is connected and coupled to a motor may thus, for example, generate a rotational movement to an instrument (5) (a root canal instrument, for example) and by this means may even convey an electric current that is capable of being utilized for the detection of the apex. The electrical connection between the motor and the handpiece (see FIGS. 2 and 3) may be effected by any connection means, for example between an attachment hook for the motor and an attachment groove (10) of a socket (11) (or by means of a telescopic button, for example). The envelope (8), which is insulating, is held by the practitioner in his hand, and its extremity at the head (4) end is placed in the patient's mouth. In this configuration, the chain of mechanical transmission and electrical component parts is constituted as follows inside the handle: the electrical current passes from the socket (11) to a fixed external race of a first bearing (12), and to a first spring (13), then to a fixed external race of a second bearing (14), then to a ring (15) that is retained axially on a first shoulder in the envelope (8), and then to a spring (16) that is retained axially by a second shoulder of the envelope (8).

The first and second bearings (12, 14) support a transmission shaft along the longitudinal axis (7) of the handle, or the first axis of the handpiece (1), and the springs (13 and 16) are compression springs of which the coils are arranged externally to the transmission shaft (7).

At this stage, the electrical current has thus crossed the handle part of the counter-angle or the handpiece (1).

As a variant, it is possible to envisage a conducting wire running from the extremity at the motor end to the contact with the instrument or tool (5).

The head (4) of the counter-angle handpiece with its second axis or drive axis (6) supports two ball bearings (with oblique contact, if possible), namely an upper bearing (17), of which the external race interacts with the second spring (16) of the handle, and a lower bearing (18), of which the axial play is taken up with the help of an elastic washer (19).

In this type of bearing assembly, the balls of the bearings are in contact at all times with the external and internal races of the latter, thereby ensuring an electrical connection between fixed parts and moving parts.

A barrel pinion (20) mounted on the drive shaft (6) comprises teeth (21) engaging with the teeth (22) of an output pinion (23) of the handle.

The barrel pinion (20) is conductive and integral with the interior races of the bearings, and it ensures the conduction of electricity to the instrument (5) and the mechanical driving of the latter. The electrical current that is conveyed to the extremity of the instrument will delimit the apex through the effect of variation in the resistance, taking into account the external insulation of the envelope (8) and a push-button (55) provided on the head (4), as described in greater detail below.

As a variant, the electrical connection between the second bearing (14) and the head (40) of the instrument is assured by an elastic and electrically conducting connecting component (88), the mechanical drive for the instrument being assured by the barrel pinion (20) as previously.

Said connecting component (88) is a strip, for example, or a bar of circular or rectangular section, and comprises a first peripheral segment (89) engaged in a slot (90) made in the race (15) of the bearing (14) and a second peripheral segment (91), at the opposite extremity to the first segment, which is supported against the head (40) of the instrument, said connecting component being maintained perpendicular to the axis of the instrument when the push-button is inactivated, thanks to the slot (90).

This variant is particularly advantageous because, on the one hand, the support on the push-button (55) has a tendency to repel the head (40) of the instrument and because, on the other hand, the contact by the connecting component with the head (40) is centered on the axis of the instrument thanks to the spherical surface of the said head, hence the rate of friction is close to zero.

Concept of the Attachment Arrangement and the Means of Tightening and Releasing of the Instrument in the Head.

What are described here are preferred, although not restrictive, embodiments of a means of attaching an instrument in the head (4) and their means of tightening and releasing the instrument.

In the course of root canal treatment, for example, the accessibility of the molars is a guarantee of comfort and quality both for the practitioner and for the patient. This is why the applicant has set herself the objective of proposing a tool-holder assembly (24) composed of mechanical transmission component parts of the head that should be as small and compact as possible.

The applicant has achieved her objective by conceiving:

-   -   a new, compact and not bulky means of tightening and releasing         (25), being part of an attachment assembly, and consisting of a         deformable and elastic belt (25) made or not made of a plastic         material (PEEK, for example), and capable by itself of assuring         the functions of tightening and releasing, said releasing being         performed by a centripetal manual action on the belt, and said         tightening being performed by relaxing this action,     -   an internal housing (26) in the head, adapted to receive the         tool-holder assembly (24) and its means of tightening and         releasing (25), said housing opening out onto the head via an         opening (27) that is capable of being closed by means of a         stopper or a cap (28), or by means of a push-button.

This solution will be appreciated more readily by reading the descriptions of the two embodiments given below.

A first mode of realization is described initially in conjunction with FIGS. 4 to 7, for which releasing is controlled by a direct manual action on the belt.

According to the housing (26) of the tool-holder assembly (24) exhibits, on the one hand, a lower, cylindrical part (29) that is coaxial with the driving axis (6) and of which the diameter is so adapted as to receive the barrel (30) of the barrel pinion (20), and, on the other hand, an upper, essentially cylindrical part (31), similarly coaxial with the driving axis (6) and having a larger diameter and intended to receive the teeth (21) of the pinion barrel with its means of interlocking the instrument as well as the device for tightening and releasing the latter described below.

The discharge opening (27) of the upper part of the housing (31) is closed by means of a stopper or cap (28), preferably although not necessarily made of the same material as the envelope (8).

The upper part of the housing (31) similarly comprises a lateral opening (32) discharging into an internal housing (33) of the handle (3), in such a way as to permit the engagement of the teeth of the barrel pinion (20) with the teeth of the output pinion (23) of the handle (3).

The barrel pinion rotates freely in the head, and its axial standard is assured between, on the one hand, the base (34) of the upper part of the housing which forms a shoulder and, on the other hand, the frontal surface (35) of the stopper. The resulting axial freedom of the said barrel pinion is in the order of a few hundred parts of a millimeter.

The rotational movement of the output pinion (23) is transmitted to the barrel pinion (20) and then to the instrument (5) thanks to a plane surface (36) provided on the instrument and interacting with a plane surface (37) provided in the internal bore (38) of the barrel pinion.

As claimed in this example of FIGS. 4 to 7, the means of tightening and releasing is composed essentially of a belt (25) made of a deformable and elastic material exhibiting a form essentially of a lozenge having a central zone (39) provided in order to retain the head (40) of the instrument securely in place at the level of an annular blocking slot (41) provided at the upper extremity of the instrument.

The large diagonal of the lozenge is provided in order to ensure that its two extremities extend diametrically beyond the envelope of the head (4) as two projections (42), each located in a notch (43) in the head, each notch (43) discharging, on the one hand, into the upper part (31) of the housing and, on the other hand, into the opening (27) receiving the stopper.

A direct, centripetal, manual action on the two projections (42) simultaneously brings about the release of the instrument, and the relaxation of this action assures the tightening of said instrument.

The flanges (44) of the notches (43) ensure the blocking against rotation of the belt, which is centered in the head by means of detachments (45) provided in the proximity of the projections (42) and supported on the periphery (46) of the upper part of the housing (26).

The axial standard of the belt is assured, on the one hand, by a shoulder (47) provided in the base (48) of an axial cavity (49) of the stopper intended to accommodate the head (40) of the instrument and, on the other hand, by the base (50) of the notches.

In this way, the belt does not touch the rotating part of the barrel pinion.

In the free state, said belt interacts with an upper shoulder (51) of the annular slot of the head of the instrument in order to bring about a first axial limitation of said instrument, the second axial limitation being assured by a plane surface (52) on the barrel pinion interacting with the transverse extremity (53) of the plane surface of the instrument.

The unlocking of the instrument involves the application of two diametrically opposed pressing forces to the projections (42), directed towards the axis of rotation. These two forces give rise to an orthogonal component, thereby releasing the instrument. The act of pressing simultaneously and directly on the two ears of the belt (with the thumb and index finger, for example) guarantees tightening at the mouth compared with the push-button system, for example. Attachment of the instrument can be effected without applying pressure to the two ears of the belt thanks to the arrangement of a conical part (64) provided on the undersurface of the central zone (39) in the belt, in conjunction with which the axial displacement of the instrument causes a radial displacement of the belt, by elasticity, and the belt resumes its form in order to assure the tightening function.

A second mode of realization of the means of tightening and releasing is described below in conjunction with FIGS. 8 to 10.

The elastic belt (25) having the form of a lozenge and a central zone (39) for the purpose of securing the instrument differs from the preceding belt by the fact that its ears (54) form projections perpendicular to the plane of the belt and are situated on the same side as the latter, and by the fact that it is maintained in position axially and radially by the barrel pinion, as illustrated in FIGS. 8 and 9.

To this effect:

-   -   the two extremities of the belt cross two peripheral gaps (61)         provided on the upper flange (62) of the barrel pinion, which         are diametrically opposed and arranged on a plane transversal to         the driving axis (6),     -   the two ears (54) are blocked against rotation by two notches         (63) on the said flange.

Furthermore, the head is distinguished from the preceding head in the sense that the stopper is replaced by a push-button (55) having a metallic insert, for example (to facilitate its manufacture).

As claimed in this mode of realization, the push-button, made of PEEK for example, exhibits a plurality of component parts:

-   -   an elastic ring (56) at the lower extremity, which restricts the         axial freedom of the barrel pinion and retains the push-button         on the head (4),     -   an intermediate elastic zone (57), which plays the role of a         return spring for the push-button,     -   an internal cylindrical insert (58), which, when the push-button         is pressed, permits the deformation of the elastic belt to be         controlled, thereby releasing the tool, and for this purpose a         press on the push-button (55) compresses its spring (57) and         causes the internal conical form (59) of the insert (58) to         interact with the complementary conical flanges (60) of the ears         of the belt.

The resulting radial component on the ears (54) of the belt induces another radial deformation perpendicular to this primary component. This deformation permits unlocking of the instrument.

The introduction of the instrument into the head may be effected by pressing on the push-button, or without pressing on the push-button, in which case a conical arrangement (64) on the undersurface of the central zone (39) of the belt permits the introduction of the instrument.

The configuration of the belt contributes to being able to guarantee the tightening through a centrifugal effect during rotation.

Concept of Push-Buttons

Miniaturization is a constant area of research in the field of medical equipment, such as the heads of the counter-angled handpieces used in dentistry. New materials, such as thermoplastic or thermosetting polymer materials, meet this challenge. Previously disclosed mechanisms may be reconsidered by taking into account the mechanical, physical and chemical characteristics of these new materials and, at the same time, by reducing the number of component parts, improving the quality and reducing the cost of the assembly; these plastic parts may be machined or injected. In addition to miniaturization, of course, these plastic materials also bring lightness, the ability to slide for dynamic equipment, high resistance to sterilization or disinfection, and favorable elastic characteristics. That is why these plastic materials can be utilized in the production of dental handpieces. The command for tightening or releasing the tool generally takes the form of the manual actuation of the push-button on the head of the handpiece. In accordance with the concept, this push-button may be integral with the dynamic assembly (rotating, vibrating . . . ), for example for endodonty, and with a fixed push-button independent of the dynamic assembly.

A head of a handpiece having a bur in place has already been presented above as an example of an application, with reference to FIGS. 2 and 3.

It should be pointed out again here that the body of a head (4), whether or not in a single piece with the handle (3), is fitted with a rotating barrel pinion (20) that is caused to rotate by an output pinion (23) in the handle. The barrel pinion possesses a freedom of rotation and an axial connection that are assured, for example, by ball bearings.

It is, of course, possible to envisage solutions without the use of ball bearings, as illustrated in FIGS. 5 and 7, having inserted plain bearings or having plain bearings molded into the body of the head.

The transmission of the rotational movement of the bur is assured by the conjugation of the plane surface (36) provided on the barrel pinion (4) and the plane surface (37) of the tool. The axial standard of the tool is guaranteed, in one sense, by the shoulder on the plane surface of the barrel pinion and by the shoulder on the complementary plane surface of the tool.

Taking this common description as the starting point, it is possible to distinguish between two types of push-button in accordance with the invention, namely:

-   -   a push-button integral with the dynamic assembly known as the         tool-holder, as indicated in FIGS. 3 and 16 by the reference         designation (55), which solution is characterized by permanent         contact between the rotating locking assembly and the         push-button. In the state of rest, the push-button (55) (made         from PEEK, for example) provides an axial limit for an elastic         split ring (65) (made from PEEK, for example) and, at the same         time, centers the latter in relation to the axis (6). The ring         (65) has an externally cylindrical form, and its internal wall         comprises an upper flange with a conical gradient (71) and an         intermediate part in the form of a transverse shoulder (66)         directed towards the axis (6). The shoulder (66) of the elastic         ring (65) retains the instrument (5) in the axial direction by         engaging in the annular slot (41). The push-button (55) is         guided radially in the bore (38) of the barrel pinion by one or         more sectors or components (87) arranged on the undersurface of         the push-button (55) and each terminated by a conical extremity         for the purpose of providing the presses on the elastic ring         (65). The axial displacement of the push-button (55) is limited         between the upper and lower extremities of one or more gaps (68)         made in the upper body of the barrel pinion, and in which         interact one or more hooks (67) provided on the undersurface of         the push-button. The elastic ring (65) applies an axial         component to the push-button (55) to return it to its initial         position. Thanks to their radial elasticity, due to slots (69)         provided between the hooks and the sectors (87), the hooks (67)         permit the “clipping” engagement of the push-button in the         barrel. A press on the push-button (55) permits unlocking of the         tool (5) by means of the conical parts (70) which engage in the         complementary conical gradient (71) of the elastic ring in order         to disengage the shoulder (66). The introduction of the         instrument (5) into the barrel pinion may take place         automatically without the need to press on the push-button         thanks to the conical part (73) provided on the undersurface of         the elastic ring at the extremity of the shoulder (66).

In FIG. 3, the means of tightening and releasing is a split elastic ring that is open along a radial plane visible on the sectional plane in FIG. 3, and the means of applying the releasing forces are constituted by the conical gradient (71).

-   -   a push-button independent of the dynamic assembly

In the position in which the tool is held in the hand, the solution is characterized by the separation of the push-button and of the locking means.

An embodiment of this kind is illustrated by way of example in FIGS. 11 to 15.

In the state of rest, whether or not in dynamic regime, and without actuation of the push-button, a conical, elastic annular clip (72), retains the tool (5) axially thanks to its arms (73) (for example 6 arms) each terminated by a shoulder (79) directed towards the axis (6). The clip (72) is integral with the rotating barrel pinion thanks to the engagement of the peripheral projections (74) of the clip in corresponding openings (76) made in the barrel pinion. An entirely transcurrent slot (77) in the clips permits the assembly and disassembly of the clip in the bore of the barrel pinion, thereby imparting the necessary radial elasticity to it.

The push-button (55) is retained axially and is centered by elastic blades (75) cut into its cap in the opening (27) in the head; these blades, when assembled under tension in the head body, offer an elastic axial freedom (along the axis 6) of the push-button.

FIGS. 12 and 13 illustrate these blades (75) in the constraint position and exhibit the clipping grooves (80) at the end of the blades for clipping the push-button (55) into the opening (27). A manual, axial press on the push-button is translated into an axial displacement of the conical base (78) of the push-button, and it then interacts with the complementary cone (82) of the internal conical cavity of the arms of the clip; releasing of the tool is then assured by the separation of the aforementioned arms and the disengagement of the shoulders (79). When the manual pressure is released, the push-button resumes its initial position, as the respective cones of the two component parts (55) and (72) are no longer in contact.

In accordance with this solution in FIGS. 11 to 15, the means of tightening and releasing is the elastic, conical clip (72), the shoulders (79) of which are adapted to engage in the groove or annular slot (28) of the instrument, and the means for applying the releasing forces and constituted by the conical internal form (82) of the said clip (72), the radial deformation of which is guaranteed by the slot (77).

Concept of Greasing

With reference to FIG. 8, which is an axial section through FIG. 9 and which shows that the head includes a cavity (83) provided around or to the side of the barrel of the barrel pinion for the purpose of containing a solid grease that is released in a small quantity on each occasion of use via an orifice (84) from the separating wall (85) between the cavity and the barrel in order to lubricate the barrel.

Assembly Concept

The envelope (8) may be produced in a single piece by molding a plastic material (for example PEEK), having electrically insulating properties, or a fritted material containing metallic inclusions (for example Metal Injection Moulding, abbreviated to M.I.M.), having electrically conducting properties, or any other material. This envelope comprises:

-   -   in the head, a first housing (26) for the attachment of a         tool-holder and an instrument along a drive axis (6), which         housing opens out to either side of the head via two openings,         of which at least one, the opening (27), exhibits dimensions so         adapted as to permit the introduction of all the component parts         of the head as well as their assembly, inside the handle, and a         second housing (33) having a rectilinear axis (7) opening out on         the one hand at the distal extremity of the handle via an         opening (81) and opening out on the other hand at the proximal         extremity of the head, in the first housing (26) via a lateral         opening (32) permitting interaction between the mechanical         components of the head and those of the handle. In addition, the         opening (81) is dimensioned in such a way as to be adapted to         permit the introduction of all the components of the handle as         well as their assembly in the interior of the latter along a         rectilinear axis referred to as the axis of the handle (7). In         order to produce a counter-angled handpiece, an envelope is         provided, of which the axes (6) and (9) form, for example, an         angle of between 90 and 180°, and preferably between 100 and         130°, and in order to produce a straight handpiece, it is         possible to stipulate that the axes (6) and (7) must be parallel         and displaced from one another in such a way as to make an         opening in the head (27) available for the assembly of the         internal component parts and the fitment of a stopper of a         push-button.

This concept is particularly advantageous because it provides the possibility of:

-   -   reducing the number of bearings, or eliminating them,     -   reducing the cost of the handpiece,     -   reducing the dimensions of the handpiece,     -   facilitating cleaning (smooth contours),     -   improving hygiene (a single piece, and no interface). 

1. A dental handpiece (1) of the type comprising mechanical components, in particular a tool-holder assembly for the attachment and rotational driving of a dental instrument about a drive axis (6) and an assembly for the transmission of movement, said mechanical components being mounted in the interior of a body (2) having a head (4) and a handle (3), characterized in that the body (2) is formed from a single piece or envelope (8), of which one part serves as a handle (3) and the other part constitutes a head, which head comprises a first housing (26) opening out with at least one opening (7) so dimensioned as to permit the introduction of the component parts of the head and their assembly in the interior of the latter, which handle comprises a second longitudinal housing (33) having a rectilinear axis (7) and opening out, on the one hand, at the extremity of the handle via an opening (81) and, on the other hand, in the first housing via a lateral opening (32), which opening (81) is so dimensioned as to permit the introduction of the internal component parts of the handle and their assembly in the interior of the latter.
 2. The dental handpiece as claimed in claim 1, characterized in that the axis (6) of the head and the axis (7) of the handle between them form a predetermined angle α for the production of a counter-angled handpiece.
 3. The dental handpiece as claimed in claim 2, characterized in that a lies between 100 and 130°.
 4. The dental handpiece as claimed in claim 1, characterized in that the axis (6) of the head and the axis (7) of the handle are parallel and are displaced from one another to permit the production of a straight handpiece.
 5. The dental handpiece as claimed in one of claims 1 to 4, characterized in that the envelope (8) is produced by molding.
 6. The dental handpiece as claimed in claim 5, characterized in that the envelope (8) is produced in polymer material.
 7. The dental handpiece as claimed in claim 6, characterized in that the envelope (8) is produced preferably in PEEK.
 8. The handpiece as claimed in one of claims 6 to 7, characterized in that it comprises electrical connection means constituted by a chain of component parts for the mechanical transmission of the rotational movement.
 9. The handpiece as claimed in claim 8, characterized in that the chain of component parts for mechanical and electrical transmission is constituted as follows: inside the handle, the electrical current passes from a socket (11) to a fixed external race of a first bearing (12), and to a first spring (13), then to a fixed external race of a second bearing (14), then to a ring (15) that is retained axially on a first shoulder in the envelope (8), and then to a spring (16) that is retained axially by a second shoulder of the envelope (8), the first and second bearings (12, 14) supporting a transmission shaft in the longitudinal axis (7) of the handle, or the first axis of the handpiece (1), and the springs (13 and 16) being compression springs of which the coils are arranged externally to the transmission shaft (7), in the head (4) of the counter-angle, with its second axis or drive axis (6) supporting two ball bearings, namely an upper bearing (17), of which the external race interacts with the second spring (16) of the handle, and a lower bearing (18), of which the axial play is taken up with the help of an elastic washer (19), a barrel pinion (20) mounted on the drive shaft (6) comprises teeth (21) engaging with the teeth (22) of an output pinion (23) of the handle, the barrel pinion (20) being conductive and integral with the interior races of the bearings, it ensures the conduction of electricity to the instrument (5) and the mechanical driving of the latter.
 10. The handpiece as claimed in one of claims 6 to 7, characterized in that the means of electrical connection are constituted by a conducting wire.
 11. The handpiece as claimed in one of claims 6 to 7, characterized in that the means of electrical connection comprise an elastic connection device (88) in order to provide the electrical connection between the mechanical transmission component parts and the head of the tool.
 12. The handpiece as claimed in claim 11, characterized in that the connecting component comprises a first peripheral segment (89) engaged in a groove (90) made in the race (15) of the bearing (14) and a second peripheral segment (91), opposite to the first segment, which is supported against the head (40) of the instrument.
 13. The handpiece as claimed in claim 5, characterized in that the envelope is produced in material of type MIM.
 14. The handpiece as claimed in one of claims 1 to 13, characterized in that the internal housing (26) in the head is adapted to receive a tool-holder assembly composed of the mechanical transmission components of the head, and to receive a means of tightening and releasing (25) the tool or instrument (5), said housing opening onto the head via an opening (27) that is capable of being closed by means of a stopper or a cap (28), or by means of a push-button.
 15. The dental handpiece as claimed in one of claims 1 to 14, characterized in that the head contains a turbine, and the body of the handpiece comprises fluid channels that are required for its function.
 16. The dental handpiece as claimed in one of claims 1 to 15, characterized in that the head exhibits a cavity intended to contain a solid grease that is released on each occasion of use via an orifice from the separating wall between the cavity and the barrel in order to lubricate the barrel.
 17. The dental handpiece as claimed in one of claims 1 to 16, characterized in that it comprises an arrangement for attaching a dental instrument to a tool-holder assembly for the attachment and rotational driving of a dental tool or instrument about a driving axis (6), said tool-holder assembly (24) being integrated into a head (4) of a dental handpiece and connected to a movement transmission assembly integrated in a handle (3) of the said handpiece (1) and composed principally of a deformable and elastic means of tightening and releasing in the form of a belt (25), of which at least one part exhibits a section adapted to engage in a groove or annular slot that is provided in the upper part of the instrument and is adapted to retain the said instrument by tightening, said means of tightening and releasing also comprising means for the application of releasing forces for canceling the tightening forces for the purpose of releasing the instrument.
 18. The dental handpiece as claimed in claim 17, characterized in that the attachment arrangement is detachable in relation to the tool-holder (24).
 19. The dental handpiece as claimed in one of claims 17 to 18, characterized in that the belt (25) made of a deformable, elastic material exhibits a form that is essentially that of a parallelogram having a central zone (39) provided for the purpose of retaining the head (40) of the instrument tightly in place at the level of a slot, the large diagonal of the parallelogram being provided in order to ensure that its two extremities extend diametrically beyond the envelope of the head (4) as two projections (42), each located in a notch (43) in the head, each of the projections constituting means for the application of forces manually and directly for releasing the belt.
 20. The dental handpiece as claimed in claim 19, characterized in that the belt (25) comprises detachments (45) provided in the proximity of the projections (42) and resting on the periphery (46) of the housing (26) of the head.
 21. The dental handpiece as claimed in claim 19, characterized in that the elastic belt (25) exhibiting the form essentially of a parallelogram and having a central zone (39) provided in order to retain the instrument tightly in place comprises two ears (54) forming projections perpendicular to the plane of the belt and situated on the same side as the latter, which two ears constitute means for the application of tightening forces via the intermediary of a barrel pinion positioned on the head of the handpiece.
 22. The dental handpiece as claimed in claim 20, characterized in that the ears comprise conical flanges (60).
 23. The dental handpiece as claimed in one of claims 19 to 22, characterized in that the belt exhibits a conical part (64) arranged on the undersurface of the central zone (39).
 24. The dental handpiece as claimed in claims 21 to 22, characterized in that the attachment arrangement also comprises a push-button exhibiting a plurality of component parts, namely: an elastic ring (56) at the lower extremity, which retains the push-button on the head (4), an intermediate elastic zone (57), which plays the role of a return spring for the push-button, an internal cylindrical insert (58), which, when the push-button is pressed, permits the deformation of the elastic belt to be controlled, thereby releasing the tool.
 25. The dental handpiece as claimed in one of claims 22 to 24, characterized in that the insert (58) comprises an internal conical form (59) in order to interact with the complementary conical flanges (60) of the ears of the belt.
 26. The dental handpiece as claimed in one of claims 17 to 18, characterized in that the deformable, elastic belt exhibits the form of a split ring (65) or a split annular clip (72) comprising an annular shoulder (66) (79) adapted to engage in an annular slot (28) in the instrument and a conical part (71) in order to interact with a complementary conical part of a push-button.
 27. The dental handpiece as claimed in claim 26, characterized in that the split ring comprises a conical part (73) provided on the undersurface of the split ring for the introduction of the instrument.
 28. The dental handpiece as claimed in claim 27, characterized in that the attachment arrangement also comprises a push-button (55) guided axially by one or more sectors (87) arranged on the undersurface and each terminated by a conical extremity (70).
 29. The dental handpiece as claimed in claim 27, characterized in that the attachment arrangement also comprises a push-button (55) comprising elastic blades (75) cut into its cap and terminated by clipping slots (80) and a conical base (78).
 30. The dental handpiece as claimed in one or other of claims 17 to 18, characterized in that the attachment arrangement also comprises a push-button for the application of releasing forces on the means of tightening and releasing.
 31. The dental handpiece as claimed in claim 30, characterized in that the push-button is integral with the tool-holder.
 32. The dental handpiece as claimed in one of claims 30 to 31, characterized in that the push-button is retained by means of a clip in an opening in the head. 